This invention relates to an improvement to a pen type code reader adapted to manually scan a sheet of recording medium such as paper and optically read the code pattern printed thereon and representing sounds, images and/or data to be processed by a computer.
Pen type code readers adapted to manually scan a sheet of recording medium such as paper and optically read the code pattern printed thereon and representing data are already known. For example, EP 0,670,555 A1 discloses a pen type code reader comprising an area sensor such as a CCD that transforms the light received from a focused image formed by an optical system into an electric signal and adapted to manually scan a sheet of recording medium such as paper, keeping its front surface having an image pick-up opening constantly in contact with the sheet of recording medium and optically read the code pattern printed thereon.
FIG. 1 of the accompanying drawings shows an exemplary code pattern that can be used with a pen type code reader of type under consideration, illustrating the physical format of dot code 1.
Referring to FIG. 1, the dot code 1, which can represent a sound data, is realized in the form of a plurality of rectangular blocks 2 arranged two-dimensionally side by side on a recording medium, each of the blocks 2 comprising a data dot pattern section 3 showing a dot image formed by white dots and black dots representing respective data values of "0s" and "1s", markers 4 arranged at the four corners of the block as reference points for locating each of the dots of the data dot pattern section 3, each of the markers 4 being formed by a certain number of consecutively arranged black dots, and a block address pattern section 5 arranged between adjacently located markers 4 to make the block 2 discriminable from other blocks 2 and including an error detecting or error correcting code.
Note that reference numeral 5A in FIG. 1 denotes the address of the block. Also note that, in the enlarged view of block 2 located in the middle of FIG. 1, the matrix of lines and the frame are shown only for the ease of understanding and do not exist in reality.
FIG. 2 of the accompanying drawings shows a schematic block diagram of the electrically functional components of a code reader adapted to optically read such a dot code 1.
Referring to FIG. 2, the code reader comprises at least an image pick-up section 6, a binarization processing section 7, a binarized image memory 8, a data restoring section 9, a demodulator section 10, and a reproducing section 11. The image pick-up section 6 includes a lighting section typically constituted by an LED, an optical system for focusing the light reflected from the dot code 1 and an area sensor, which may be a CCD, for picking up the light focused by the optical system. The binarization processing section 7 carries out a processing operation of binarizing the image pick-up signal output from the image pick-up section 6 by means of predetermined binarization threshold value. The binarized image memory 8 stores binarized image data produced from the binarization processing section 7. The data restoring section 9 reads the binarized image data stored in the binarized image memory 8, detects the dots of the dot code and assigns "0" or "1" to each of the detected dots to restore and output the data. The demodulator section 10 demodulates the data output from the restoring section 9. The reproducing section 11 reproduces the original data, which can be sound data, after processing the output of the demodulator section 10 for error correction and data expansion.
The image pick-up section 6 of the code reader is moved on the dot code 1 in the direction indicated by the arrow in FIG. 1 to pick-up the image of the dot code on a section by section basis so that the code reader can read the dot code 1 if the latter is greater than the viewing field 6A of the image pick-up section 6.
In other words, the original data can be restored from the data sections of the blocks 2 even if the dot code 1 cannot be picked up by the code reader in a single shot, provided that the address of each of the blocks 2 is correctly recognized by the code reader. Thus, consequently, a large volume of information, which can be sound information, can be stored highly densely on and transmitted by a sheet of paper to such an extent that cannot be realized by any conventional one-dimensionally or two-dimensionally arranged bar codes. Such a dot code system may find a variety of applications.
When reading the data stored in the binarized image data from the binarized image memory 8 and detecting the dots, the restoring section 9 firstly detects the markers 4 in the binarized image data and determines a reference point for reading the dots on the basis of the centroid of each of the detected markers 4. Then, it detects the central pixel of each dot in the data dot pattern section 3 by referring to the reference point for reading the dots and determines if the detected dot is a white dot or black dot so that either "0" or "1" is assigned to the detected dot.
Thus, if the highly densely printed dot code is geometrically distorted to make it defective to some extent, it may be read properly and appropriately and the original data can be restored reliably.
The recorded original data, which can be sound data, is modulated when it is transformed into a dot code 1. The demodulator section 10 is provided to demodulate the modulated data.
The original data is modulated such that the restoring section 9 can easily detect the markers to begin its operation. More specifically, the largest possible number of consecutive black dots in the dot code pattern section is made smaller than the number of consecutive black dots of each marker 4 for the input sound data so that the image of each of the dots in the data dot pattern section 3 may be discriminated from that of each of the markers 4.
If the largest diameter of a marker 4 is equal to the length of five black dots printed in the data dot pattern section 3 and arranged on a line along a given direction, the above modulating operation will be such that the number of consecutive black dots in the modulated data is made smaller than five.
However, while a pen type code reader as disclosed in EP 0,670,500 A1 is portable and can be handled conveniently for reading a code pattern, the code reader main body 12 of the pen type code reader is apt to be tilted toward the scanning direction, or the longitudinal direction of the code pattern 13 (as indicated by the arrow in FIG. 3), during a manual scanning operation so that the front end of code reader main body having the image pick-up opening is lifted from the contact surface and the code pattern 13 is put out of focus. Then, it is no longer possible to accurately pick up the image of the code pattern 13 to consequently give rise to read errors for the dot code.
Additionally, a pen type code reader of the type under consideration requires an arrangement that makes the front end of the code reader main body to be easily aligned with the code pattern and protects the code pattern against damages and stains that can be produced when it is brought into contact with the front end of the code reader main body.